These excerpts from a very recent article in a medical journal
provide excellent quotations. To clarify, teratology is the
study of the cause of birth defects.
From Biogenic Amines Vol 19, No 2, pp97-145 (2005)
Also available at: www.vsppub.com 'The future of teratology research in vitro', Jarrod Bailey,
Andrew Knight and Jonathan Balcombe.

Abstract - Birth defects induced by maternal exposure to
exogenous agents during pregnancy are preventable, if the agents
themselves can be identified and avoided. Billions of dollars
and man-hours have been dedicated to animal-based discovery and
characterisation methods over decades.

We show here, via comprehensive systematic review and analysis
of this data, that these methods constitute questionable science
and pose a hazard to humans.

Mean positive and negative predictivities barely exceed 50%;
discordance among the species used is substantial; reliable
extrapolation from animal data to humans is impossible, and
virtually all known human teratogens have so far been identified
in spite of, rather than because of, animal-based methods'.
We argue that the poor performance of animal-based teratology
alone warrents its cessation; it ought to be replaced by the
easier, cheaper and more repeatable EST [a cell-based test], and
resources made available to improve this and other tests even
further.'